scholarly journals Globular cluster formation and evolution in the context of cosmological galaxy assembly: open questions

2018 ◽  
Vol 474 (2210) ◽  
pp. 20170616 ◽  
Author(s):  
Duncan A. Forbes ◽  
Nate Bastian ◽  
Mark Gieles ◽  
Robert A. Crain ◽  
J. M. Diederik Kruijssen ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Globular Clusters ◽  
Cluster Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Future Research ◽  
Chemical Abundances ◽  
Multiple Populations ◽  
Open Questions ◽  
Formation And Evolution

We discuss some of the key open questions regarding the formation and evolution of globular clusters (GCs) during galaxy formation and assembly within a cosmological framework. The current state of the art for both observations and simulations is described, and we briefly mention directions for future research. The oldest GCs have ages greater than or equal to 12.5 Gyr and formed around the time of reionization. Resolved colour-magnitude diagrams of Milky Way GCs and direct imaging of lensed proto-GCs at z ∼6 with the James Webb Space Telescope (JWST) promise further insight. GCs are known to host multiple populations of stars with variations in their chemical abundances. Recently, such multiple populations have been detected in ∼2 Gyr old compact, massive star clusters. This suggests a common, single pathway for the formation of GCs at high and low redshift. The shape of the initial mass function for GCs remains unknown; however, for massive galaxies a power-law mass function is favoured. Significant progress has been made recently modelling GC formation in the context of galaxy formation, with success in reproducing many of the observed GC-galaxy scaling relations.

scholarly journals Star-cluster formation and evolution

2006 ◽  
Vol 2 (S237) ◽  
pp. 230-237 ◽  
Author(s):  
Pavel Kroupa
Keyword(s):  
Galaxy Formation ◽  
Cluster Formation ◽  
Star Clusters ◽  
Mass Function ◽  
Cluster Mass ◽  
Cluster Evolution ◽  
Stellar Component ◽  
Galaxy Formation And Evolution ◽  
Dynamical Time ◽  
Formation And Evolution

AbstractStar clusters are observed to form in a highly compact state and with low star-formation efficiencies, and only 10 per cent of all clusters appear to survive to middle- and old-dynamical age. If the residual gas is expelled on a dynamical time the clusters disrupt. Massive clusters may then feed a hot kinematical stellar component into their host-galaxy's field population thereby thickening galactic disks, a process that theories of galaxy formation and evolution need to accommodate. If the gas-evacuation time-scale depends on cluster mass, then a power-law embedded-cluster mass function may transform within a few dozen Myr to a mass function with a turnover near 105M, thereby possibly explaining this universal empirical feature. Discordant empirical evidence on the mass function of star clusters leads to the insight that the physical processes shaping early cluster evolution remain an issue of cutting-edge research.

scholarly journals The Formation and Evolution of Star Clusters and Galaxies

2005 ◽  
Vol 13 ◽  
pp. 347-349
Author(s):  
Stephen E. Zepf
Keyword(s):  
Galaxy Formation ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Near Infrared ◽  
Cluster Formation ◽  
Star Clusters ◽  
Elliptical Galaxies ◽  
Cluster Systems ◽  
Important Observation ◽  
Formation And Evolution

AbstractThis paper addresses the questions of what we have learned about how and when dense star clusters form, and what studies of star clusters have revealed about galaxy formation and evolution. One important observation is that globular clusters are observed to form in galaxy mergers and starbursts in the local universe, which both provides constraints on models of globular cluster formation, and suggests that similar physical conditions existed when most early-type galaxies and their globular clusters formed in the past. A second important observation is that globular cluster systems typically have bimodal color distributions. This was predicted by merger models, and indicates an episodic formation history for elliptical galaxies. A third and very recent result is the discovery of large populations of intermediate age globular clusters in several elliptical galaxies through the use of optical to near-infrared colors. These provide an important link between young cluster systems observed in starbursts and mergers and old cluster systems. This continuum of ages of the metal-rich globular cluster systems also indicates that there is no special age or epoch for the formation of the metal-rich globular clusters, which comprise about half of the cluster population. The paper concludes with a brief discussion of recent results on the globular cluster – low-mass X-ray binary connection.

DARK MATTER IN THE GALAXY

1994 ◽  
Vol 03 (supp01) ◽  
pp. 53-61
Author(s):  
ROSEMARY F.G. WYSE
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Galactic Disk ◽  
Brown Dwarfs ◽  
Mass Function ◽  
Initial Mass Function ◽  
Solar Neighborhood ◽  
Vertical Force ◽  
Chemical Abundances ◽  
Stellar Objects

I will first review the evidence that our Milky Way Galaxy contains a substantial amount of dark matter, and what is known about the spatial distribution of this material, from rotation curve decompositions and from analysis of the vertical force law in the solar neighborhood. All data are consistent with no significant unidentified material in the Galactic disk, requiring that the dark matter be in a spatially-extended distribution. Brown dwarfs, or sub-stellar objects, are often discussed as possible dark-matter candidates, especially in view of the implication from nucleosynthesis calculations that dark baryons exist. The somewhat discour-aging status of recent searches for brown dwarfs is reviewed, together with present understanding of the low-mass stellar initial mass function. I discuss a long-term survey of the motions and chemical abundances of Galactic stars which will provide constraints on the Galactic potential well and the history of Galaxy formation.

scholarly journals Modeling Formation of Globular Clusters: Beacons of Galactic Star Formation

2010 ◽  
Vol 6 (S270) ◽  
pp. 381-384
Author(s):  
Oleg Y. Gnedin
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Cluster Formation ◽  
Star Clusters ◽  
Mass Function ◽  
Giant Molecular Clouds ◽  
Early Galaxies ◽  
The Masses

AbstractModern hydrodynamic simulations of galaxy formation are able to predict accurately the rates and locations of the assembly of giant molecular clouds in early galaxies. These clouds could host star clusters with the masses and sizes of real globular clusters. I describe current state-of-the-art simulations aimed at understanding the origin of the cluster mass function and metallicity distribution. Metallicity bimodality of globular cluster systems appears to be a natural outcome of hierarchical formation and gradually declining fraction of cold gas in galaxies. Globular cluster formation was most prominent at redshifts z > 3, when massive star clusters may have contributed as much as 20% of all galactic star formation.

scholarly journals A Review of the Theory of Galactic Winds Driven by Stellar Feedback

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 114 ◽  
Author(s):  
Dong Zhang
Keyword(s):  
Galaxy Formation ◽  
Mass Function ◽  
Future Research ◽  
Star Forming ◽  
Stellar Feedback ◽  
Galactic Winds ◽  
Galaxy Formation And Evolution ◽  
Supernova Explosions ◽  
Formation And Evolution ◽  
Magnetohydrodynamic Simulations

Galactic winds from star-forming galaxies are crucial to the process of galaxy formation and evolution, regulating star formation, shaping the stellar mass function and the mass-metallicity relation, and enriching the intergalactic medium with metals. Galactic winds associated with stellar feedback may be driven by overlapping supernova explosions, radiation pressure of starlight on dust grains, and cosmic rays. Galactic winds are multiphase, the growing observations of emission and absorption of cold molecular, cool atomic, ionized warm and hot outflowing gas in a large number of galaxies have not been completely understood. In this review article, I summarize the possible mechanisms associated with stars to launch galactic winds, and review the multidimensional hydrodynamic, radiation hydrodynamic and magnetohydrodynamic simulations of winds based on various algorithms. I also briefly discuss the theoretical challenges and possible future research directions.

scholarly journals Star Clusters Near and Far

2020 ◽  
Vol 216 (4) ◽  
Author(s):  
Angela Adamo ◽  
Peter Zeidler ◽  
J. M. Diederik Kruijssen ◽  
Mélanie Chevance ◽  
Mark Gieles ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Globular Clusters ◽  
High Redshift ◽  
Cluster Formation ◽  
Star Clusters ◽  
Local Universe ◽  
Stellar Feedback ◽  
Formation And Evolution ◽  
Numerical And Analytical Methods ◽  
Fundamental Units

Abstract Star clusters are fundamental units of stellar feedback and unique tracers of their host galactic properties. In this review, we will first focus on their constituents, i.e. detailed insight into their stellar populations and their surrounding ionised, warm, neutral, and molecular gas. We, then, move beyond the Local Group to review star cluster populations at various evolutionary stages, and in diverse galactic environmental conditions accessible in the local Universe. At high redshift, where conditions for cluster formation and evolution are more extreme, we are only able to observe the integrated light of a handful of objects that we believe will become globular clusters. We therefore discuss how numerical and analytical methods, informed by the observed properties of cluster populations in the local Universe, are used to develop sophisticated simulations potentially capable of disentangling the genetic map of galaxy formation and assembly that is carried by globular cluster populations.

Multiple populations in globular clusters: New insights from chemical evolution and horizontal-branch models

2019 ◽  
Vol 14 (S351) ◽  
pp. 321-323
Author(s):  
Young-Wook Lee ◽  
Jenny J. Kim ◽  
Sohee Jang ◽  
Chul Chung ◽  
Dongwook Lim ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Globular Clusters ◽  
Mass Function ◽  
Significant Loss ◽  
Blast Waves ◽  
Initial Mass Function ◽  
Evolution Model ◽  
Asymptotic Giant Branch ◽  
Horizontal Branch ◽  
Multiple Populations

AbstractIn order to investigate the origin of multiple populations in globular clusters (GCs), we have constructed new chemical evolution models for proto-GCs where the supernova blast waves undergo blowout without expelling the ambient gas. Chemical enrichments in our models are then dictated by the winds of massive stars together with the asymptotic-giant-branch stars ejecta. We find that the observed Na-O anti-correlation can be reproduced when multiple episodes of starburst and enrichment are allowed to continue in proto-GCs. The “mass budget problem” is mostly resolved by our models without ad-hoc assumptions on star formation efficiency, initial mass function, and significant loss of first-generation stars. Interestingly, ages and chemical abundances predicted by this chemical evolution model are in good agreements with those independently obtained from our stellar evolution model for the horizontal-branch. We also discuss observational evidence for the GC-like multiple populations in the Milky Way bulge.

scholarly journals INFRARED STUDIES OF THE STELLAR CONTENT IN EXTRAGALACTIC SYSTEMS

1981 ◽  
Vol 96 ◽  
pp. 297-316
Author(s):  
Marc Aaronson
Keyword(s):  
Galaxy Formation ◽  
Globular Clusters ◽  
Near Infrared ◽  
Formation Rate ◽  
Absolute Magnitude ◽  
Type Systems ◽  
Morphological Type ◽  
Mass Function ◽  
Initial Mass Function ◽  
Stellar Content

Normal galaxies emit most of their radiation longward of one micron, and many problems related to our understanding of galaxy formation and evolution can be fruitfully addressed with measurements at near-infrared wavelengths. Such problems include the make-up of the red stellar population, the star formation rate, the initial mass function, metallicity effects, and mass-to-light ratio. How these various quantities depend on morphological type, on total mass (or absolute magnitude), on radial position, and on environment is also of great interest. In this review recent infrared observations of extragalactic stars, star clusters, and galaxies having important bearing on these questions are discussed. Particular emphasis is placed on new evidence for the presence of a finite intermediate age population in early-type systems. This evidence comes from observations of intermediate age stars in many Magellanic Cloud globular clusters, observations of such stars in at least one nearby dwarf spheroidal (Fornax), the difficulties of fitting theoretical isochrone models to the red V-K colors of E and SO galaxies, and the differences in the infrared color-magnitude relations for the Virgo and Coma clusters.“It is not very bright to measure a blue magnitude for a red object.”– Vera Rubin

Dynamical effects on the stellar mass function of multiple stellar populations in globular clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 346-349
Author(s):  
Enrico Vesperini ◽  
Jongsuk Hong ◽  
Jeremy J. Webb ◽  
Franca D’Antona ◽  
Annibale D’Ercole
Keyword(s):  
Globular Clusters ◽  
First Generation ◽  
Cluster Formation ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Stellar Mass ◽  
Initial Mass Function ◽  
Cluster Center ◽  
Mixing Rate ◽  
Multiple Population

AbstractWe present a brief summary of the results of a study of the effects of dynamical evolution on the stellar mass function of multiple-population globular clusters. Theoretical studies have predicted that the process of multiple-population cluster formation results in a system in which second-generation (2G) stars are initially more centrally concentrated than first-generation (1G) stars. In the study presented here, we have explored the implications of the initial differences between the 2G and 1G structural properties for the evolution of the local (measured at different distances from a cluster center) and global mass function. We have studied both systems in which 1G and 2G stars start with the same initial mass function (IMF) and systems in which 1G and 2G stars have different IMFs. Finally we have explored the evolution of the spatial mixing and found that the multiscale nature of the clusters studied leads to a dependence of the mixing rate on the stellar mass.

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